The objectives of the proposed project are to study: (1) the effect of acute and chronic administration of a chemical carcinogen (1,2-dimethyl-hydrazine) on the proliferation, differentiation and migration of epithelial cells in the mouse colon; and (2) the formation of adenomatouspolyps and adenocarcinomas induced by the chemical. Radioautographs prepared from Epon-embedded colonic tissues of mice given H3-thymidine will be employed primarily for the analysis of cell population kinetics of the colonic epithelium in animals treated with the carcinogen and in chemically induced neoplasms. The purpose is to study polypogenesis and carcinogenesis in the colon with respect to disturbances in cell proliferation and differentiation.